The polymerization of aromatic vinyl monomers including styrene during processing is a matter of concern, because it causes formation of unwanted polymers and results in loss of yield of end product and makes the process un-economical.
In the art use of inhibitors and retarders, and combination thereof to overcome problem of polymerization of styrene has been reported.
The problem of using the inhibitors alone is that these are to be added continuously or at regular interval, because once they are consumed, the polymerization will re-start.
The problem of using the retarders alone is that these are not very effective to reduce polymerization of styrene to a level of substantial inhibition or to the acceptable level of inhibition.
The prior art proposes composition comprising a combination of (a) a quinone methide (QM) and (b) 4 hydroxy tempo 2,2,6,6-tetramethyl-,1-oxide (4HT) as styrene polymerization inhibitor. However, the inventor has found [refer to examples and corresponding data] that main problem of using this known composition of QM and 4HT is that even with higher amounts of the composition, the problem of polymerization is not resolved.
The prior art also proposes composition comprising a combination of (a) a quinone methide (QM) and (b) a phenolic compound, for example 2,6-di-tert-butyl phenol (2,6 DTBP) as styrene polymerization inhibitor. However, the inventor has found [refer to examples and corresponding data] that main problem of using this known composition of QM and 2,6 DTBP is that even with higher amounts of the composition, the problem of polymerization is not resolved.
Therefore, the industry is aiming for additive composition wherein the amount of QM and phenolic compound can be reduced or minimized so that the resulted composition is economical as well as safe for human being.
Any effort to reduce or minimize consumption of QM and/or phenolic compound will lessen the problems of the industry.